HEDGEROWS are the focus of much natural activity this month.

Birds are singing from their tops and building nests within, while insects are buzzing around the newly emerged flowers around hedge bottoms.

There are also things going on with the trees that make up the hedge itself.

Hedges were originally invented by our ancestors as field boundaries – barriers to keep farm animals in and wild animals out.

They did this by selecting a line of trees and cutting partway through each tree trunk without killing it, then bending each one over to fill the gap between it and its neighbour – a process now known as hedge-laying.

Not surprisingly, trees with sharp, spiky twigs were good at the job, so consequently most of our hedges are made up of two species with particularly unwelcoming foliage… hawthorn and blackthorn.

Both trees take the second part of their name from very sharp ended growths on all of their growing twigs – the thorns.

Although both are ferocious, of the two the black’s thorns are reputedly worse because they are longer and thinner, so more likely to break off in a wound and cause allergic reaction or infection.

So common is this phenomenon in farmers and gardeners that doctors have a name for it – cystic blackthorn granuloma.

The thorniness of both trees has led to a legendary Easter connection. Both have been suggested as the source of the crown of thorns used on Jesus prior to his crucifixion, as described in Matthew’s Gospel.

There are lots of other equally thorny candidates growing in the Mediterranean region, but if it was one of these two then hawthorn is the more likely candidate as it is a far more common plant in modern Israel.

Religious festivals apart, these two trees are famously visible in Ryedale at this time of year. Although both trees’ beautiful white flowers are uncannily alike, the two species cannot be confused because they flower and leaf at different times.

In April, blackthorn bushes are blanketed in drifts of flowers but have not got round to growing leaves yet, whereas hawthorns have started to sprout leaves but not flowers.

By next month, the blackthorns will have lost their flowers, but grown leaves while the hawthorns will earn their alternative name of May blossom as they are then covered in thousands of blooms.

This separation of flowering time has probably evolved to avoid competition for pollinators.

Hawthorn and blackthorn often grow side-by-side in hedgerows and there are only so many bees and hoverflies around at any one given time.

It does seem to me that poor old blackthorn drew the evolutionary short straw in being the earlier flowerer of the two.

There are far fewer pollinators around in April than in May and always the chance of a late frost to kill the emerging flower buds.

Fortunately, that hasn’t happened this year (yet!) which bodes well for next Christmas.

If you’re wondering what next Christmas has got to do with anything then here is my logic; I always enjoy a glass or two of home-made sloe gin around Christmas time having collected the necessary sloes from my local hedgerows in late October.

Sloes are the fruits of the blackthorn tree that have developed during the summer from those April flowers so every flower lost to a late hard frost means one less sloe in Autumn.

In 2008, a freezing cold April caused a nationwide failure of the sloe crop and some commercial producers of sloe gin almost went out of business.

Last year wasn’t good either but it’s thought that the cause this time was a fungus disease brought on by a wetter summer than normal. It seems like there’s no escaping the vagaries of British weather!